From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793404602; b=uw7Rklrn2bwqbBg8v1rTBH2U6CcWaaq8X801zeRX8MB0sj7MsJrXocxiHfr2dH9koPeM GuCNa+gkeac5t4qwviG8M+KlVjmdGueZ2UZgqJ6kRTyhPC2TEZp3cFqrYFlQ6O77DCHi3 neQHlUxP+N9NRf60rBtt6I/AcmdOjbQly2ApF7V/j8TI7DmGFsM/CXThCbZM/jyoiF1II uYFY5jGLlFfqxcpI7b/vtbuh7VPuGeg2SmjDYGI6c2Sdw2M4Ie7jGKGs+JFsAhInYdgv2 IeUvNsFaLVhTaFyO+L8Q5a1BvWbIdCep663iH3hMabr4sym5Y9/A8WyF2k1UROSqFmg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793404602; h=Received:DKIM-Signature:Date:From:To:Cc:Subject:Message-ID: References:MIME-Version:Content-Type:Content-Disposition:In-Reply-To; bh=BDaHsLTeFS9uNn3ux2fwusgfE2J5PsxVZUwAq3RoQ60=; b=InmaIEE4GIpFzjoAorH88wsgC34JLem03HDDluqD6+ut2kyP2P9gHgU7BrcVC7cFwfVU H56y7dlSZRLL/YCv3LQ8/8WiqenHlfK+IrwaGwsHzwdwWTwETcnxtPDkgd8dMpw90V18f C3bwuJtvi/yC+PaVGNy44QcDkiG0LPrkE/VfWt0DB2Vywx6D5hIdMeL1s45QpWwLJ+pwC RmQh8cTJ6q9BfzumEHuy4MoORZR/7aziHQKRmmnFdStwSp0ZAqaW3pvuJBH3uuDKV8hwm RF6xc7+QHsvTl/efX7ll96XUyO3RMDhKkGq0GL+Tj92Y0qjYzG9ZK3/OzG/dEMlpNww== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=U3cWys8N; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4F9EA606A31D for ; Fri, 30 Oct 2026 23:56:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=U3cWys8N Received: by smtp.kernel.org (Postfix) with ESMTPSA id CD4BE1F000C1; Fri, 30 Oct 2026 23:56:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793404602; bh=BDaHsLTeFS9uNn3ux2fwusgfE2J5PsxVZUwAq3RoQ60=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=U3cWys8NzRoR5iji4VbwnppP2F99hQ09nWZ2HYE+r0avE7eTlictybnZyKKAwL5kZ fJHD9+5VXqMHbofiQzrm0wGvGx8GiEBtL+AhyD53fY5PqBQWsAdfGmwIDs2/SnrnSI tE4g4FQtkLP1D0ayza/GkEF4Q5h7Mpk2OzpqvAPkCqXjjoSMjFC99mpXQNsMxFzh2X UIc4tt3snwnZw9HwgJYT6TWS03nimGOfvfPEblWg2yDoHpLNW5lL9f7/zeEaN4MdFt h/FvI6hZ7XBVO/kLZlUaTBuEAdvb5XsPUOwzSKqjP+WpInh1m5yMnw2f1wc+OatjOB j+uez14nOkGLg== Date: Fri, 30 Oct 2026 13:56:40 -1000 From: Tejun Heo To: Peter Zijlstra , Ingo Molnar , Juri Lelli , Vincent Guittot Cc: Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , K Prateek Nayak , linux-kernel@vger.kernel.org Subject: Re: [PATCH sched/urgent] sched/deadline: Fix stale rq->dl_server after a server pick returns RETRY_TASK Message-ID: References: <20261030221842.4071610-1-tj@kernel.org> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261030221842.4071610-1-tj@kernel.org> On Fri, Oct 30, 2026 at 12:18:42PM -1000, Tejun Heo wrote: > __pick_task_dl() records the server in rq->dl_server whenever the server's > pick returns non-NULL, RETRY_TASK included. __pick_next_task() clears > rq->dl_server at its top, but a RETRY_TASK restarts the pick below that > clear. put_prev_set_next_task() then hands the stale server to whatever the > restarted pick takes. > > Since b3a2dfa8b42e ("sched/fair: Add newidle balance to pick_task_fair()"), > fair_server_pick_task() returns RETRY_TASK when the newidle balance released > the rq lock and a higher class task was enqueued meanwhile. > > That task, an RT task for example, then carries the fair server in > p->dl_server until it is next put. The RV deadline monitors see the fair > server switch in with it, and core scheduling, if enabled meanwhile, treats > the task as deadline priority. > > Don't record the server when its pick returns RETRY_TASK. The restarted pick > records whichever server it goes through, if any. > > Verified with a synthetic reproducer. > > Fixes: b3a2dfa8b42e ("sched/fair: Add newidle balance to pick_task_fair()") > Signed-off-by: Tejun Heo Ugh, please ignore this one. Sent out the wrong patch. I'll test Juri's. Thanks. -- tejun